1. Field of the Invention
The present invention relates to a device which can produce a wink in a telephone system. More specifically, the present invention is directed towards a device which, upon seizure of a telephone line by a central office, simulates the presence of a PBX unit by producing a wink to acknowledge the seizure.
2. Description of the Prior Art
When companies set up a telephone system which requires multiple extensions, it is not uncommon to reserve a block of telephone numbers from the local telephone provider, e.g., all numbers from 555-1000 through 555-1250. In this setup, the provider routes all calls to those numbers to an on-site PBX (Private Branch exchange). The PBX transfers any calls to the appropriate station (phone) inside the company which are connected to the PBX. A simplified block diagram of such a PBX system is shown in FIG. 1.
The system shown in FIG. 1 operates as follows. When an outside party calls one of the dedicated numbers, the telephone company central office seizes the line connected to the PBX unit; as known to those in the art, the seizure is induced by shorting the Tip and Ring lines. The PBX acknowledges the seizure by inducing a wink, in which the polarity of the two lines of the PBX are reversed. The central office acknowledges the wink by sending the last three or four digits of the phone number (depending on the amount of reserved lines) to the PBX. The PBX then routes the call to the dialed station.
A drawback of the PBX system described above is that if the central office does not receive a wink from the PBX system, it will not transmit the digits, or other data. Thus, if the PBX has not yet been installed, or is otherwise inoperable, a wink cannot be induced from the PBX site. Further, since PBX's are large, bulky, and expensive, it is not practical for installers and/or repair crews to carry a spare PBX as part of their equipment. Accordingly, the prior art to date does not provide any device which can simulate a PBX wink at a remote location.